Remove auto-generated stuff

Having these files committed to Git just causes them to appear as
changed every time a developer runs things like `./autogen.sh`.

In some cases, the changes are as pointlessly annoying as:

  -# Makefile.in generated by automake 1.13.1 from Makefile.am.
  +# Makefile.in generated by automake 1.13.4 from Makefile.am.
Ignore the built stuff
Update to the code in Git v1.8.5.1
Merge pull request #3 from bochecha/update

Update to the xdiff code from Git v1.8.5.1